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A universal, unconventional petroleum system exists throughout our solar system
Oil present in extraterrestrial environments is derived from living organisms through processes very close to those at work on Earth.
24 July 2009, SPIE Newsroom. DOI: 10.1117/2.1200907.1699
Observations of geologically ancient terrestrial sediments show that reduced carbon commonly survives in fossiliferous organic remains as a large (macro) molecule called kerogen. We have seen ample evidence preserved in sedimentary rocks—over three billion years old—of hydrocarbons (the basic chemical component of petroleum) derived from primitive organisms such as archaea and prokaryotes. The substances are preserved as solid bitumen, hydrocarbon-fluid inclusions (globules), and inert carbon transformed from liquid hydrocarbon exactly as found in various Paleozoic to Cenozoic terrestrial oil and gas fields. Consequently, there is no reason to believe that this so-called Archean oil and pyrobitumen originated any differently than normal crude oils. We explore whether a similar process might satisfactorily account for the diverse types of organic matter present in an important class of meteorites known as carbonaceous chondrites (CCs).
Previous reports of petroleum-like hydrocarbons in CCs,1–4 as well as recent findings of these compounds by NASA, suggest that they are common constituents within our solar system. For example, Saturn's moon Titan contains a liquid-methane lake and huge clathrate-rich (gas hydrate) zones. These zones exist on Saturn's other moons as well, and possibly also within the the planet's rings. Anthony Zuppero5 has proposed that such extraterrestrial fuels might provide major feedstock for space-transportation schemes moving throughout the solar system. In addition, our earlier studies of CCs6 support those of other researchers7–11 as regards the existence of biogenic (i.e., produced by life processes) organic remains. To date, however, no study has simultaneously looked at both organic and inorganic components of these meteorites in the light of their terrestrial counterparts.
Figure 1. Scanning-electron-micrograph (SEM) image of a sample from the carbonaceous meteorite Orgueil showing a framboidal (named for its raspberry-like appearance) magnetite cluster (center) in the midst of clay minerals and amorphous mineral-lipid groundmass (abundant in aliphatic and aromatic hydrocarbons, fluorescent in blue-light excitation under an incident-light microscope). Other than solid bitumen, no structurally preserved macerals (organic remnants) are visible. % Random bitumen or vitrinite-like reflectance (Ro) =0.70.
(a) SEM image of a sample from the carbonaceous meteorite Murchison showing partially mineralized organic remnants. (b) EDS carbon map and (c) sulfur map of the same remnants. In 2004, the group of Hoover described this type of organic component as a well-preserved bacterial cell with possible flagella.8
% Ro = 1.21.
The results of our current research, which focuses on the geochemistry of CCs, reveal a fascinating story. Specifically, we geochemically analyzed selected CCs (ALH 840001, Allende, Dofar 735, EET, Murchison, NWA 3003, Orgueil, Tagish Lake, and Vigarano) to determine the dominant organic components within these extraterrestrial rocks.6 Our analyses are primarily based on organic petrology, scanning-electron-microscopy energy-dispersive x-ray spectroscopy (SEM-EDS), and pyrolysis/gas chromatography/mass spectrometry (GC/MS) techniques. We discovered that the Murchison, Orgueil, and Tagish Lake CCs are rich in organic compounds (mostly >1.5% total organic carbon), containing abundant semisolid and solid bitumen with variable proportions of microbial-like remnants and their biodegraded macerals associated with framboidal iron oxides and sulfides, and claylike minerals (see Figures 1–5). Algal-like and lignin (an organic polymer)-rich polyaromatic macromolecular organoclasts have also been detected, especially in Murchison and Dofar.6
Figure 3. SEM image of a sample from the carbonaceous meteorite Vigarano showing partially mineralized organic remnants (the elevated oval body with a small attachment at the southeast that is possibly a bacterial remnant). (inset) EDS image of various elements present within the organic body. Al: Aluminum. Au: Gold. Ca: Calcium. C: Carbon. Fe: Iron. Mg: Magnesium. Ni: Nickel. O: Oxygen. Si: Silicon. % Ro = 5.1.
Figure 4. (left) Evidence of nanobacteria partially replaced by minerals in the Orgueil CC (SEM) and (right) elemental distribution within the nanobacteria (EDS). S: Sulfur. % Ro = 0.70.
Figure 5. (left) Evidence of organic remains (possibly bacterial bodies: central part of the SEM image) from the ALH 840001 CC partially replaced by minerals. (right) EDS image of elements present in the same region of the organic remains. % Ro = 3.25.
On the basis of our analysis, we propose that these hydrocarbons (oil and solid bitumen) originated through biological processes similar to those at work in terrestrial organic-rich sedimentary rocks. Confirming the work of earlier researchers, in the CCs we studied, the hydrocarbons appear to be derived from nanobacteria and/or primitive algal remains (based on SEM-EDS, visual kerogen analysis using fluorescence, and white-incident-light microscopy). The extraterrestrial rocks contain abundant alkanes (normal, cyclo-, and isoalkanes), alkyl aromatics, some polycyclic aromatic hydrocarbons, thiophenes, and nitrile compounds (especially within Tagish Lake and Orgueil) with biological signatures (i.e., chemical components detectable in modern plants and animals in a degraded form). We further propose that there has been a transformation of biopolymers to various forms of hydrocarbons (oil and solid or liquid bitumen) through the geopolymeric stages typical of such processes on Earth. We have carried out thermal modeling of organic remains. The results are particularly important from an environmental perspective insofar as they indicate the existence of two temperature-influenced categories of organic compounds important in the evolution of CCs.6
First, low temperature—a projected maximum of <200°C—acted on organic remains to form oil, gas, and some asphaltene (e.g., Murchison, Orgueil, and Tagish Lake). Geochemically these CCs are remarkably close to oil-prone kerogen type II and II–III source rocks that usually occur close to major oil and gas fields within the terrestrial environment. Hence, we consider that these low-temperature meteorites were formed in relatively cold and humid areas within the early solar system, comets, and interstellar-dust areas where microbial-like and slightly evolved organic communities could have developed (see Figures 1, 2, and 4). The temperature effect of cosmic-radiation flux would have helped promote the formation of hydrocarbons from the kerogen macromolecule. Comets are particularly chemically complex, reactive environments that may have served to incubate primitive life forms and may be the precursors of some CCs. It is therefore not surprising to find that the key life-forming elements carbon, hydrogen, oxygen, nitrogen, and sulfur are all present in comets, just as they are in CCs. Comets are cosmic nuclei of chemical disequilibria within which carbon-based life, with its inherent entropy-reducing (i.e., order-promoting) properties, can disprove a nonbiological origin of these organic remains and their transformation products.
Second, high temperature (>200°C) induced organic remnants (mainly pyrobitumen and inert kerogen, especially within Allende, ALH 840001, EET, and Vigarano). It is possible that these traces of organic matter originated within a superheated (hydrothermal) environment similar to the habitat within hydrothermal vents along terrestrial midoceanic ridges. Even in such an extreme environment, biological life and hydrocarbon generation are intimately linked (see Figures 3 and 5. In this context, we can clearly demonstrate that the kerogen macromolecule and derivative hydrocarbons occur in certain CCs evidently as a result of the degradation of bacterial clusters or primitive algal remains. These biological precursors may also have been preserved in comets and other cool environments within our solar system, just as they were in some terrestrial Archean environments.12
In summary, we have described what we call a biologically derived, universal, unconventional petroleum system.6 On the basis of our findings, we believe there to be the prospect of oil and gas throughout the solar system, including on Mars and various moons of Saturn. Should this hypothesis bear out, hydrocarbons recovered from Earth's sister planets and their moons could potentially contribute toward the food and energy needs of humans colonizing extraterrestrial environments. It would also confirm that Earth is not the only cosmic body to possibly support life in diverse forms. As our next steps, we plan to continue our research on CCs and comet dust until samples from Mars become available. In addition to current techniques, we intend to dye CC samples and analyze them using special fluorescence and tunneling-electron microscopies to chemically identify bacteria and other forms of organic remains.
Prasanta K. Mukhopadhyay
Head Office, Global Geoenergy Research Ltd.
Prasanta ‘Muki’ Mukhopadhyay has 25 years of research experience in the genesis of organic matter in both terrestrial and extraterrestrial environments, which includes application of organic petrology and petroleum geochemistry in prospect evaluation for both conventional (in particular deep-water geochemistry) and unconventional (shale gas, coalbed methane, and gas hydrate) hydrocarbons.
David J. Mossman
Geography and Environment Department
Mount Allison University
New Brunswick, Canada
James M. Ehrman
Digital Microscopy Facility
Mount Allison University
New Brunswick, Canada
2. K. A. Kvenvolden, J. G. Lawless, K. Pering, E. Peterson, J. Flores, C. Ponnamperuma, I. R. Kaplan, C. Moore, Evidence for extraterrestrial amino acids and hydrocarbons in the Murchison meteorite, Nature 228, pp. 923-926, 1970.
9. D. S. McKay, E. H. Gibson, Jr., K. L. Thomas-Keprta, H. Vali, C. S. Romanek, C. S. Clemett, X. D. F. Chillier, C. R. Maechling, R. N. Zare, Search for past life on Mars: possible relic biogenic activity in Martian meteorite ALH 840001, Science 273, pp. 924-930, 1996.